Lubkicant additives



United States Patent '0 This invention relates to lubricant additives and their preparation.

The excellent lubricating properties of molybdenum compounds have been known for some time. Difiiculties have, however, been encountered in attempts to use them as additives in liquid lubricants. These difiiculties are due primarily to the general insolubility and high spei cific gravity of molybdenum compounds. As a result, attempts to use them as additives to liquid lubricants have been more or less limited to formulations for suspending them in oils. Unfortunately, however, such suspensions generally have poor stability because of the high specific gravity of the suspended material.

We have found that phosphomolybdic acid, a compound that is well known as containing molybdenum in sexivalent form, and salts thereof with an organic nitrogen base, can be reduced by reaction with an organic compound to a form in which at least a part of the molybdenum is tetravalent, and that the resulting products possess a very appreciable solubility in an excess of the reducing agent as well as in other chemically related organic compounds. It is surprising that the reduction can be carried out with any organic compound having an active hydrogen in the molecule.

Theorganic compounds that are suitable for the reduction of phosphomolybdic acid and salts thereof include higher alcohols, esters, glycols and polyalhylene glycols as well as organic nitrogen bases, which can have multiple functions as reducing agents, neutralizing agents, stabilizing agents and further as diluents.

It is advantageous 'to use, as reducing agents, organic compounds which, by reason of their molecular structure, are soluble in mineral oils or other liquid lubricants or which have lubricating properties of their own. Inasmuch as phosphomolybdic acid as well as its complex reduction products after treatment with most organic reducing compounds are acidic and therefore corrosive, it is desirable to use the salts of phosphomolybdic acid with organic nitrogen bases rather than phosphomolybdic acid per so as a starting material, or to neutralize the acidic products obtained by reduction of phosphomolybdic acid with other organic reducing compounds such as alcohols. Organic nitrogen bases can therefore advantageously be employed in several ways, e.g., to neutralize phosphomolybdic acid and form a salt thereof to be used as a starting material, whereupon a different organic compound such as an alcohol is used as a reducing agent; as a reducing agent for the phosphomolybdic acid, in which instance the organic nitrogen base is preferably used in excess and accomplishes neutralization and reduction; and for neutralizing and heat stabilizing the acidic reaction product of phosphomolybdic acid with a nonbasic organic reducing compound, such as an alcohol. It is to be understood of course that the organic nitrogen bases can be used for more than one of these functions.

It is surprising that all known organic nitrogen bases that are soluble in or at least compatible with liquid lubricants are suitable for use in neutralizing and reducing phosphomolybdic acid, and for neutralizing and enhancing the thermal stability of an acidic reaction product of phosphomolybdic acid with a non-basic reducing agent. The extent to which the final reaction products of phos phomolybdic acid with organic nitrogen bases can be 'ice used as additives for lubricants depends upon the particular use to which the lubricant is to be put and on the particular conditions thereof such as the nature of the bearing surfaces, temperature and pressure. The same is true'also for molybdenum complexes containing nonbasic organic reducing compounds which may themselves be lubricants. The organic compounds, including organic nitrogen bases, must of course be at least compatible with the liquid lubricants to which the ultimate product is to be added.

The organic nitrogen bases that are suitable for neutralizing the acidity of phosphomolybdic acid and of the products obtained by reducing the acid with non-basic organic reducing compounds in order that the final additive will not be corrosive to bearing surfaces include such high molecular weight amines as oleylamine; -dioleyl amine; oleyloxyethylglyoxalidine; dehydroabietylamine; N arninopropylmorpholine; di 2 ethylhexylamine; Armeen 2T,'believed tb be a mixture of secondary amines R NH in which the Rs are 30% hexadecyl, 25% octadecyl, and 45% octadecenyl; Duomeen C, believed to be a mixture of N-alkylpropylene diamines of the formula RNHC H -NH in which R is a mixture of satu rated alkyl radicals containing eight, ten, twelve, sixteen and eighteen carbon atoms and unsaturated eighteen carbon atom alkyl radicals, the C alkyl radicals being predominant; and Armeen SD, believed to be a mixture of primary hexadecyl, octadecyl, octadecenyl, octadecadienyl amines. These basic nitrogen compounds may also, as indicated earlier, be used as reducing agents for reducing the valence of at least some of the molybdenum from six to four and converting the complex acid or reaction product into a lubricant-soluble state.

Non-basic organic compounds that are suitable for reducing the valence of the molybdenum from six to four and rendering it lubricant-soluble and which are themselves either soluble in lubricants or are lubricants per se include such higher alcohols, esters, glycols and polyalkylenc glycols as ethylhexanediol, a term intended to include the various isomers. thereof including Z-ethyl- 1,6-hexanediol; Abitol, a mixture of 15% dehydroabietyl alcohol, 40% dihydroabietyl alcohol and 45% tetrahydroabietyl alcohol; Eutanol, a highly refined liquid mixture of predominantly animal origin containing four-teen to eighteen carbon atoms; normal octadecanol; the dioctyl esters of adipic acid; benzylbutyl phthalate; Ucon 504-18660, a water-soluble polyalkylene glycol; Ucon DUB-67E, a water-insoluble polyalkylene glycol; Ucon -1-11400, a polyalkylene glycol reported to have a specific gravity of 20/ 20 C. of 1.093; polyethylene glycol; dibutoxytetraglycol, C4H90 C2H40)4C4Hg Flfixol C17H15OOCCH(CH2OCH2)XCH2COOC17H15 having a viscosity of 25.1 cp. at 20 C.; and Flexol CC-55, C H [COOCH CH(C H5)GAE-I 1 To convert the phosphomolybdic acid into an effective lubricant additive in accordance with the method of the invention, the acid or a salt thereof with a basic organic nitrogen compound, is heated to an elevated temperature above C. and preferably to between 100 and C. with one or more organic reducing compounds of the type described. This heat treatment is carried out until a deep blue color is obtained to indicate completion of the reaction.

In one preferred embodiment, the organic reducing compounds selected for use are those having lubricating properties of their own. The reaction products, thus obtained can be added tomore of the same lubricants or to other compatible lubricants to adjust the molybdenum concentration to a preselected level. The organic reducing compounds that are particularly useful in this embodiment include, e.g., polyalkylene glycols, their ether or ano es a "7 {J ester derivatives, dicarbox-ylic acid esters and higher alcohols.

The molybdenum concentration can vary within wide limits and is ordinarily selected on the basis of the ultimate use of the lubricant being formed. It is generally preferable to adjust the initial content of phosphornolybdic acid or its salts to about 0.1 to by Weight based on the total weight of lubricant.

The organic reducing compounds need not be used in precise stoichiometric amounts. They can be used in considerable excess, especially when the reaction products are to be used in mineral oil-based lubricants. In this embodiment, higher alcohols containing ten to eighteen carbon atoms such as dodecanol, hexadecanol and dehydroabietylalcohol are entirely suitable. Eutanol and amines such as oleylamine, dioleylamine, dehydroabietylamine, N-aminopropylrnorpholine, di-2-ethylhexy1amine and dialkylthioureas, as Well as amino alcohols such as oleyloxyethylglyoxalidine and/ or mixtures thereof are most effective as reducing agents.

The concentrates thus obtained, which may contain from to 40% of a lubricative molybdenum compound, depending upon the quantity of reducing agent used, increase the lubricating efliciency of liquid lubricants, particularly of mineral oils, in which they are dissolved. They are eminently useful as cutting oils, bearing oils, engine break-in oils, and the like.

If a lubricant is to be subjected to extreme pressures during operation, it may be advisable to introduce sulfur or a sulfur compound before actual use of the lubricant to facilitate reaction in situ of molybdenum and sulfur to form molybdenum disulfide. If desired, the sulfur introduced for this purpose may be contained in the reducing compounds used in accordance with the invention for the purpose of reducing the molybdenum from the sexivalent to the tetravalent state and rendering it more soluble in the ultimate lubricant. Sulfur compounds that are suitable for this purpose are, for example, sulfurized unsaturated higher fatty acids and their esters, fatty alcohols, amines, olefinic polymers, organic sulfides and disulfides such as benzylsulfide, dibenzylsulfide, diphenyldisultide as well as xanthates of diols and glycols or dialkylthiourea and phosphorusand sulfur-containing products such as the derivatives of thiophosphoric acid and dithiophosphoric acid, e. g., zinc dihexyldithiophospha-te. These and equivalent sulfur-containing compounds are preferably used in proportions of about 0.1 to 5% by weight, based on the combined weight of lubricant.

These and other embodiments of the invention as well as the effectiveness of the additives will become further apparent from the following examples.

Example 1 Thirty percent by weight of phosphomolybdic acid were added to each ofthe following materials at room temperature:

Eutanol Abitol The solutions were heated to 125 C., becoming green 4; upon splitting 'off water. Further heating to 140 C. caused them to become a deep blue. The solutions were maintained at 140 C. for four days. They were all stable in that no precipitate formed.

Example 2 0.05 mol of each of the followin amines:

Dehydroabietylamtine Armeen 2T Arrneen SD N -arninopropylmorpholine Dioleylthiourea were dissolved in acetone and admixed, while stirring, with 1/140 mols phosphomolybdic acid, likewise dissolved in acetone. A partial precipitation of the resulting phosphomolybdic acid salts took place. Complete recovery of the reaction products was eifected by removal of the solvent at C. at reduced pressure.

Five grams of each of the salts thus obtained were heated to 150 C. with 10 grams Eutanol. After a total of ten minutes, deep blue solutions were formed which were then subjected to stability tests at C'. It was found that after standing for two weeks at this temperature there was no visible precipitation of the salts.

Similar tests have been conducted successfully with Abitol, dibutyoxytetraglycol, Ucon 75-H1400 and a polyethylene glycol having a molecular weight of approximately 500.

Example 3 Part A.--A mixture of one p.b.-w. (parts by weight) dehydroabietylamline salt of phosphomolybdic acid and 7 p.b.w. Eutanol, prepared as described in Example 2, was added as a concentrate to 92 p.b.w. of a parafiinic raffinate having a viscosity of 17 E. at 50 C. Precipitation of the concentrate began only after the solution had been held at 120 C. for thirty-six hours.

Part B.ln the mixture of Part A, one p.b.w. of the mineral oil was replaced by one p.b.w. of Armeen 2T. The mixture was stable for more than ten days at 120 C, showing no precipitation.

Part C.-Five parts of the 30% concentration of phosphomolybdic acid in a mixture of unsaturated ten to eighteen carbon atom alcohols of Example 1 were mixed with 95 parts of a naphthenic spindle oil raffinate having a viscosity of 2 E. at 50 C. Upon standing at C., it began to become cloudy after twenty-four hours.

Part D.Two parts of a sulfurized dioleylarnine containing one mol of sulfur per mol of amine were added to the solution described in Part C. The stability was found to be increased to a showing of no precipitation after standing at least eight days at 110 C.

Example 4 Several tests were carried out on an Almen Wieland machine (AWM) and a four-ball machine (FBM). The lubricants tested and the results thereof are shown in the table below, in which the term sulfurized Eutanol indicates a stoichiometric ratio of one mol Eutanol to 0.5 mol sulfur:

1 Continuous operation.

The data in the table shows that the test results on both machines are improved by the presence of the acidic reaction product of free phosphomolybdic acid as well I Part A.A lubricating mixture was prepared by adding one part of a Rosin Amine D-phosphomolybdate in 3 p.b.w. Abitol and '3: p.b.w. Eutanol to 93 p.b.w. of a naphthenic railinate having a viscosity of 17 E. at 50 C.- This mixture was found tobe stable for three days at 110 C. and then slowly became cloudy.

Upon testing on the Almen Wieland machine under continuous operation at a load of 11500 logs, a constant friction coefiicient of 0.133 was measured. The four-ball machine test indicated 170/180 legs.

Part B.One-hal-f part of the naphthenic raifinate of the mixture of Part A was replaced by an equal amount of Armeen 2T. The stability at 110 C. was thereby increased to at least ten days and the mixture was no longer corrosive to ferrous and non-ferrous metals. In continuous operation on the Almen Wieland machine with a 1500 kg; load, a constant coefiicient of friction of 0.125 was made. The four-ball value was 180/ 190 kg.

Parr 'C.-One-half of the naphthenic rafiinate of the mixture in Part A was replaced by an equal amount of sulfurized Armeen 2T, the sulfur content being one mol per mol of Armeen. as in Part B but thernixture was found to be somewhat corrosive to non-ferrous metals. At constant operation on an Almen Wieland machine at 1500 kgs. load, a coeflicient of friction of 0.13 was measured. The four-ball value was increased to 240/260 kg. I

Part D.A lubricating mixture was prepared by adding a concentrate containing 0.7 p.b.w. phosphomolybdic acid, 1.3 p.b.w. dioleylthiourea and 6 p.b.w. Abitol to 92 p.b.w. naphthenic raflinate having a viscosity of 17 E. at 50 C. The mixture remained stable for eight days at 110 C. and showed slight corrosive action with non-ferrous metals.

' Under continuous operation on an Almen Wieland machine at a load of 1500 kgs, a coefiicien-t of friction of 0.12 was measured. The four-ball value was 230/240 kg.

Two oils were prepared which ditfered from one another only in the amount of sulfur in the form of zinc Both oils were found to be stable for founteen days at 110 C. and neither of them showed any corrosion on ferrous or non-ferrous surfaces. The Almen Wieland' value was determined with regular bearings and the coefficient of friction of both oils under continuous operation at loads of 1500 kgs. was found to be 0.12. Another test run with hardened bearings showed no materially different behavior, both oils showing a load capacity of up to 2500 kgs. with equal friction curves. The four-ball values of oils A and B,however, were 160/170 and 240/260 kgs., respectively,

showingan increase due to the presence of sulfur.

. I The two oils were further subjected to the Niemann test for hypoid gear oils. Oil A reached eight load levels with a specific wear of between 0.1 and 0.2 mgs. per horse- It was slightly corrosive to ferrous and non-ferrous metals.

The heat stability was the same h 6 power hour whereas oil B endured twelve load levels, which is the maximum possible with this test. The specific wear was between 0.05 and 0.1 mgs. per horsepower hour. Weclaim:- q I 1. A method which comprises heating (A) a member of the group consisting of phosphomolybdic acid and a salt thereof with an organic nitrogen base of the group consisting of oleyloxye thylglyoxalidine, N-aminopropylmorpholine and primary and secondary hydrocarbon and hydrocarbon racyl amines with (B) an organic reducing compound of the group consisting of high molecular weight alkylene glycols, abietyl alcohols, alkyl alcohols, carboxylic acid esters and poly-alkylene glycols having at least eight'c'arbon atoms to a temperature between about and C. until the reactants assume a deep blue color, the amount of reactant B beingjsufficient to reduce at least a part of the molybdenum to tetravalent form. 2. The method defined in claim 1 wherein the organic reducing compound has lubricating properties.

3. The method defined in claim 1 in which the organic reducing compound is used in excess of the amount stoichiometrlcally required to reduce the valence of the molybdenum therein from six to four.

-N-arninopropylmorpholine and primary and secondary hydrocarbon and hydrocarbon acyl amines of 8 to 18 carbon atoms and reducing the resulting salt with an organic reducing compound of the group consisting of high molecular weight alkylene glycols, abietyl alcohols, alkyl alcohols, carboxylic acid esters and polyalkylene glycols having at least eight carbon atoms at a temperature between about 100 and 150 C. until the reactants assume a deep blue color.

6. A method which comprises heating phosphomolybdic acid with an amount of an organic nitrogen base of the group consisting of oleyloxyethylglyoxalidine, N-amino- .propylmorpholine and primary and secondary hydrocarbon and hydrocarbon acyl amines of 8 to 18 carbon atoms in stoichiometr-ic excess of the amount required to form a neutral salt thereof for neutralizing and reducing said acid to a non-corrosive, lubricant-solu-ble state.

7. A method which comprises heating phoisphomolybdic acid with a non-basic organic reducing compound of the group consisting of high molecular weight alkylene glycols, abietyl alcohols, alkyl alchols, carboxylic acid esters and polyalkylene glycols having at least eight carbon atoms to a temperature between about 100 and 150 C. until the reactants assume adeep blue color and become lubricant-soluble, and neutralizing said reduced product by reaction with an organic nitrogen base of the group consisting of oleyloxyethylglyoxalidine, N-aminopropylmorpholine and primary and secondary hydrocarbon and hydrocarbon acyl amines 8 to 18 carbon atoms.

8. The product prepared by the method defined in claim 1.

9 The product defined in claim 8 wherein the organic nitrogenbase contains sulfur.

, 10. A lubricating oil selected from the group consisting of mineral and polyalkylene glycol lubricating oils containing about 0.1 to 5% by weight of an additive prepared by the method defined in claim 1.

11. The product prepared by the method defined in claim 1 wherein the organic reducing compound is ethyl hexanediol.

12. The product prepared by the method defined in 4 claim 11 wherein (the organic reducing compound is a dioctyl diester 0f adipic acid.

13. The product prepared by the method defined in claim 1 wherein the organic reducing compound is a dioctyle diester of 'suberic acid.

14. The product prepared by the method defined in claim 1 wherein the organic reducing compound is benzylbutyl phthalate.

15. A product prepared by heating a salt of phosphornolybdic acid and N-arninopropylmorpholine with dibutoxytetraglycol to a temperature between about 100 and 150 C. until the reactants assume a deep blue color.

16. A product prepared by heating a salt of phosphomolybdic acid and N-aminopr-opylmorpholine with a polyethylene glycol having :a molecular Weight of about 5 00 to a temperature between about 100 and 150 C. until the reactants assume a deep blue color.

w References Cited in the file of this patent UNITED STATES PATENTS 2,788,258 Arnold et a1 Apr. 9,1957 2,852,469 Hugel Sept. 16, '1958 2,900,235 Arnold 'et al Aug. 18, 1959 OTHER REFERENCES Liebotf: Reduction of Phosph omolybdic Acid by Mon-omethyl-p=Amino Phenol, Chem. Abstracts 25:

T schopp et -al.: The Reduction of Phosphomolybdic Acid to Molybdenum Blue, Chem. Abstracts 26: 51128,

Bamann et al.: A New Reaction at the Naphthionic 15 Acid Molecule, Chem. Abstracts 47: 99491, 1953. 

1. A METHOD WHICH COMPRISES HEATING (A) A MEMBER OF THE GROUP CONSISTING OF PHOSHOMOLYBDIC ACID AND A SALT THEREOF WITH AN ORGANIC NITROGEN BASE OF THE GROUP CONSISTING OF OLEYLOXYETHYLGLYOXALIDINE, N-AMINOPROPYLMORPHOLINE AND PRIMARY AND SECONDARY HYDROCARBON AND HYDROCARBON ACYL AMINES WITH (B) AN ORGANIC REDUCING COMPOUND OF THE GROUP CONSISTING OF HIGH MOLECULAR WEIGHT ALKYLENE GLYCOLS, ABIETYL ALCOHOLS, ALKYL ALCOHOLS, CARBOXYLIC ACID ESTERS AND POLYALKYLENE GLYCOLS HAVING AT LEAST EIGHT CARBON ATOMS TO A TEMPERATURE BETWEEN ABOUT 100 AND 150*C. UNTIL THE REACTANTS ASSUME A DEEP BLUE COLOR, THE AMOUNT OF REACTANT B BEING SUFFICIENT TO REDUCE AT LEAST A PART OF THE MOLYBDENUM TO TETRAVALENT FORM.
 10. A LUBRICATING OIL SELECTED FROM THE GROUP CONSISTING OF MINERAL AND POLYALKYLENE GLYCOL LUBRICATING OILS CONTAINING ABOUT 0.1 TO 5% BY WEIGHT OF AN ADDITIVE PREPARED BY THE METHOD DEFINED IN CLAIM
 1. 